1. Field of the Invention
The present invention relates to a recording and/or reproducing apparatus using such a recording medium as an optical disk, an optical and magnetic disk, a magnetic disk, or the like.
2. Description of the Prior Art
While such recording media as optical disks, optical and magnetic disks, and so forth have become widely used, there are two systems for controlling rotation of these disks: the constant linear velocity system (CLV system) and the constant angular velocity system (CAV system). In the CLV system, the angular velocity is gradually reduced as the head moves radially from the inside of the disk to the outside thereby to keep the linear velocity always constant, and this CLV system affords a larger data recording volume than that with the CAV system which controls the angular velocity to be kept always constant. Because uniform recording density is achieved thereby, the CLV system provides another merit that such factors for the recording and/or reproducing circuit as that for waveform equalization need not be varied.
Generally speaking, however, the structure of the servo circuit for controlling the rotation of the disk by the CLV system is more complex than that by the CAV system. Namely, the rotation control circuit in the CLV system is so arranged that coarse controlling of the number of revolutions of the spindle motor is made depending on the reproducing position of the head on the disk and finer controlling, in addition, is made to keep the period of a clock signal in the data reproduced from the disk at a predetermined value. Besides, if the preset linear velocities are different from disk to disk for the reason that the manufacturers of these disks are different or other reason, then it will become necessary to provide a disk recording and/or reproducing apparatus with the control information in accordance with each disk from outside.
When it is attempted to record or reproduce a data signal on or from disks which are set at different linear velocities using the same recording and/or reproducing apparatus, as stated above, the user has to input necessary control information to the apparatus from outside referring to operation manuals or the like each time a disk is loaded into the apparatus.
When it is required, as hithertofore, to provide from outside a recording and/or reproducing apparatus with control information necessary for attaining rotation control at a constant linear velocity each time a disk is set on the apparatus, not only is it troublesome to confirm the control information for each disk, but also there are risks of erroneous control information to be input.